4)CHARGE: Battery charging indicator. When the charging current is higher than 0.3A, it will be illuminated. 5)VOLT: Voltage adjustment potentiometer.6)AMP: Current adjustment potentiometer. 7)10 A output fuse. Reverse connection will cause the fuse to blow. At this time there is no output voltage; after correcting the connection and changing another fuse, it can continue to work.